Use the Light Group Editor to add or remove lights in a light group.
Revit enters light group edit mode. The Light Group panel displays in the drawing area. (You can drag it to the desired location or place it on the ribbon. Model elements and lighting fixtures that belong to another light group display in halftone. Lighting fixtures that belong to the selected light group display in green. Lighting fixtures that are not currently assigned to a light group display normally.
A reflected ceiling plan in light group edit mode
Revit highlights lighting fixtures that are not currently assigned to a light group. All other model elements continue to display as halftone, indicating that you cannot select them.
When you select a lighting fixture, Revit displays it as green to indicate that it is being added to the group.
The lighting fixtures that are currently assigned to a light group display as green.
After you select a lighting fixture, it displays normally, indicating that it is no longer part of the group.